Horizontal directional drilling is a method of boring horizontally underground for the use of utility installations and remediation. Horizontal directional drilling boring rigs are used to drill a bore without the use of trenches. These boring rigs consist of a boring machine, drill pipe or drill string, and a boring head attached to the front of the drill string. Locating electronics or other instruments are placed within a housing near the boring head. In operation, a bore path is plotted and laid out for the drill string to follow. A beacon such as a transmitter provides a locating signal for detecting the underground position of the boring head. After the boring head has successfully followed a path under the obstacle and continued to bore to a desired length, the boring head can be removed and the utility installed by towing it into the ground behind a backreamer.
The housing is located between the boring head and the drill string and supports the beacon. There are generally three types of beacon housing designs: end loaded, side loaded, and partial opening side loaded. In an end load beacon housing, the beacon is loaded from one end of the housing and mates with a clocking mechanism located within a cavity of the housing. The clocking mechanism orients the beacon within the cavity in the proper position of rotation and secures the beacon in the housing. The problem with end load housing is that the process of installing the beacon and securing it to the clocking mechanism is done blindly, making it difficult to ensure the beacon correctly mates with the clocking mechanism. Another problem often encountered is removing the beacon from the end loaded housing. Epoxy is typically used to fill the transmission slots to keep debris and fluid out of the beacon housing and away from the beacon. The epoxy may eventually breakdown and crack allowing sand and debris to enter the housing and pack around the beacon. When this occurs it can become difficult to remove the beacon from the housing.
Side load beacon housing allow the beacon to be installed through an opening on the side of the housing that is the same length and width as the beacon. The beacon may be inserted parallel with the housing and indexed to the clocking mechanism such that the beacon may properly record and transmit the orientation of the boring head and deliver proper signals. While the side load housing allows the transmitter beacon to more easily be installed in the housing, the problem exists that the door covering the side opening may deteriorate and dislodge from the housing. When this occurs, the beacon becomes exposed and often falls out of the housing becoming damaged beyond repair. The other problem with the side load housings are that they only allow for one or two water ports to direct fluid from the back of the housing to the front, making it hard to use side load housings with larger boring machines.
A partial opening side load housing, described in U.S. Pat. No. 7,600,582, is a side load design but with an opening with a length less than the length of the transmitter. This design reduces the risk of losing the transmitter beacon if the side load door dislodges from the housing. However, drillers that want to bore longer and deeper typically prefer the more durable end load housing mechanisms.